How to Use and Enable/Disable 'Safe Mode' in Windows 8

If you want to boot into Safe Mode to try and fix any issue, you need to enable it manually because it doesn't come enabled in Windows 8 by default.
To enable and use Safe Mode, follow the inline steps:
1. Click Start and click Search.
2. Type cmd and press Enter. cmd.exe appears in the results list.
3. Right-click on cmd.exe. An Advanced icon displays on the lower, right corner of the screen.
4. Click on Advanced icon and select Run as administrator. The User Account Control dialog box gets displayed.
5. Click Yes to continue.
6. Type bcdedit /enum /v on the command prompt and press Enter.
7. Type bcdedit /copy on the command prompt but this time do not press Enter.
8. Now, you need to add the identifier of the Windows Boot Loader with a description. For this scroll down to the Windows Boot Loader display. Right-click and select Mark from the popup menu. It will highlight the identifier. Press Enter to copy it
9. Go to the command prompt where you typed the command, right click and select Paste from the popup menu. The identifier gets copied after that command.
10. Press Space and type /d "Windows 8 Developer Preview (Safe Mode)" and press Enter to execute the whole command i.e. (bcdedit /copy identifier (copied) /d "Windows 8 Developer Preview (Safe Mode)"
11. Type Exit and press Enter to close command prompt
12. Again go to Start >> Search and type msconfig and press Enter.
13. System Configuration dialog box gets displayed, click on Boot tab
14. Select Windows 8 Developer Preview (Safe Mode) from the list and check Safe boot check box in Boot options section
15. Click OK. A dialog box appears that asks you to Restart.
16. After Restart, select Windows 8 Developer Preview (Safe Mode) to boot into it.
In the Safe Mode, Windows will directly boot into Desktop view. You can fix the issue your pc has here.

To disable the Safe Mode option, you need to delete the Safe Mode option from the boot options.
1. Repeat steps 1 to 5 as in enable Safe Mode.
2. At the command prompt enter bcdedit / delete, but do not press Enter yet.
3. Repeat steps 8 to 10 as in enable Safe Mode.
4. The message “The operation completed successfully” appears on the command prompt.
Notes
For Safe Mode, Windows 8 Developer Preview should be installed.
You can also turn off Safe Mood if you uncheck Safe Boot check box for the Windows 8 Developer Preview.